Railway traffic controlling apparatus



July 4, 1961 c. D. IHRIG 2,991,352

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed April 21, 1958 4Sheets-Sheet 1 1, R INVENTQR. laffopd D. [/znqq E BY A] .A

HIS 14 JJOHIVE'Y July 4, 1961 c. D. lHRlG RAILWAY TRAFFIC CONTROLLINGAPPARATUS 4 Sheets-Sheet 2 Filed April 21, 1958 Avg July 4, 1961 c. D.lHRlG RAILWAY TRAFFIC CONTROLLING APPARATUS 4 Sheets-Sheet 3 Filed April21, 1958 SIWWW km INVENTOR. clam! 12. 1121 4 MAW 1275 14 TTOH/VEY July4, 1961 c. D. lHRlG RAILWAY TRAFFIC CONTROLLING APPARATUS 4 Sheets-Sheet4 Filed April 21, 1958 H m n m m w m m a m u m E W m m mm m m w m m M11m n m MQRRNN MSQNN MSQSN ESQ? United Sttes My invention relates torailway trafiic controlling apparatus and particularly to an arrangementof apparatus for use in a single track, two direction, stretch ofrailway track provided with normally energized reversible coded trackcircuits with reverse code supplied to the rails of the track during theoff periods of the normal code.

In railway trafiic control systems, manually controlled signals forgoverning the movements of trains over a stretch of railway track aresometimes separated by a considerable distance. Under such circumstancesit is usually expedient to provide one or more sets of automaticintermediate signals within said stretch of track in order to allow forfollowing train movements and thereby expedite the movement of trainsthrough the stretch. In such a stretch of railway track where codedtrack circuits are used in lieu of line conductors for control of thesignals, it is sometimes desired to supply reverse code to the rails,during the off periods of the normal code, to effect approach lightingof the intermediate signals and thereby conserve power, or to obtainapproach application of cab signal energy to the rails at theintermediate signal locations.

Under the above described conditions, means must be provided at theintermediate signal locations to distinguish whether normal code orreverse code is being received from the rails of the track stretch inorder to prevent an intermediate signal from clearing against anopposing train movement. It is accordingly one object of my invention toprovide an arrangement of apparatus at each intermediate signal locationto obtain such distinction between normal and reverse code.

Other objects and characteristic features of my invention will becomeapparent as the description proceeds.

In accomplishing the foregoing objects of my invention, I employ at eachintermediate signal location a slow release relay for distinguishing thecode received. This relay is energized when normal code is received overthe rails from one direction and is retained energized while reversecode is being received over the rails from the opposite direction.Contacts of this relay are used for prevention of clearing the improperintermediate signal, as will become apparent hereinafter in thisdescription.

I shall describe one form of apparatus embodying my invention, and shallthen point out the novel features thereof in claims.

Referring to the accompanying drawings, FIGS. 2 through 5, when arrangedas shown in FIG. 1, illustrate a stretch of railway track over whichtrains may move in either direction, and provided with normal andreverse coded track circuits employing apparatus of my invention. FIG. 2illustrates the left or westbound end of the stretch of railway trackprovided with a signal lEG, manually controlled as will hereinafter bedescribed, and associated apparatus for controlling the movement oftrains in an eastwardly direction over said track stretch. FIG. 4illustrates the right or eastward end of the track stretch and amanually controlled signal ZWG and associated apparatus for controllingtrain movements in a westwardly direction over the stretch. FIGS. 3 and5 illustrate a set of automatic signals and associated apparatus locatedintermediately between said controlled signal locations. Theseintermediate signals are designated tent lWG and 2EG and control trainmovements past said location in westwardly and eastwardly directions,respectively.

The stretch of railway track between signals IEG and ZWG is divided intoa westward and an eastward track section designated IT and 2T,respectively. Track section 1T extends from signal lEG to theintermediate signal location and track section 2T extends from saidlocation to signal 2WG. Each of these track sections is provided withcoded track circuits, the structure and operation of which will be madeapparent as the description proceeds. However, for present purposes itshould be pointed out that track relays IETR, IWTR, ZETR, and ZWTR areassociated with the rails of the track stretch at the west end of tracksection 1T, the east end of track section 1T, the west end of tracksection 2T, and the east end of track section 2T, respectively. Thesetrack sections are separated from each other, and from the stretches oftrack to the west and east of signal locations l'EG and ZWG,respectively, by insulated rail joints shown in the drawings in theconventional manner by lines drawn perpendicularly across each of thelines representing the rails of the track stretch.

It is believed expedient to point out at this time that energy for theoperation of the apparatus at each signal location, except the codedtrack circuits, is furnished by a suitable source of direct current suchas a battery of proper voltage and current. For the purposes ofsimplicity these sources are not shown in the drawings, but theirpositive and negative terminals are identified by the referencecharacters B and N, respectively. Energy for operation of the codedtrack circuits are shown in the drawings, in the conventional manner, asbatteries designated lTBW, lTB-E, ZTBW and ZTBE located at signallocations IEG, 1WG, ZEG and ZWG, respectively.

The above named track relays as well as several other relays shown inthe drawings have the letters CF shown in the rectangles representingthe windings of the relays. These letters are used to designate codefollowing relays, that is relays which are picked up when a code pulseis supplied to their windings and released when the code pulse isremoved. The contacts of these relays are shown with their movablemembers in both up and down positions with one position beingrepresented by a solid line and the other position being represented bya dotted line. These contacts are shown in this manner to indicate thattheir associated relay is a code following relay and the solid linerepresents the normal condition of the associated relay. That is, if thesolid line represents the up position of a contact its associated relayis following normal code, and if the solid line represents the downposition of a contact its associated relay is not following normal code.As previously stated the track circuit system employed with my inventionis a normally energized reversible coded track circuit system and isnormally coding in the direction from east to west as Will be more fullyoutlined further on in this specification. Therefore, the code followingrelays with their contacts shown in the up position, that is with thesolid lines of the movable members of the contacts representing the upcontact position, are the relays that are normally following normalcode.

Referring now to FIG.4 of the drawings, there is shown a trafiic leverdesignated FL which controls the direction of traffic through the trackstretch between signals lEG and ZWG. This lever controls the pickup orrelease of a lever repeater relay NLPR accordingly as the lever is inits right or left position. When lever FL is in its right or R positiona circuit is completed for picking up relay NLPR which extends forterminal B of the battery over contact a of the lever in its R positionand through the winding of the relay to terminal N of the battery. Thepickup ofrelay NLPR by the lever in its R position conditions theapparatus at signal ZWG location to apply normal code to track section2T for a train movement from left to right through the track stretchshown in the drawings. As previously set forth this is the normalcondition of the system shown. The movement of lever FL from its Rposition to its left or L position releases relay NLPR, removes thenormal code from track section 2T, and initiates a reversal of thetraffic controlling system as will be described.

There is also shown in FIG. 4 track relay 2WTR, previously mentioned,and relays 2WCR, ZWTFPR, 2WHR, and a code generating relay 75CTRC. Thelatter relay is constantly energized by battery terminals B and Nconnected directly to its winding and operates its contacts at a speedof 75 operations per minute to generate what is commonly termed 75 code.Such relays are commonly called code transmitter relays and are wellknown in the art.

Relay ZWCR controls the application of reversal or normal code to tracksection 2T at signal 2WG location. As previously stated, under thenormal status of the system normal code is being transmitted from signallocation 2WG. To accomplish this transmission relay 2WCR is beingintermittently picked up and released by a circuit which extends fromterminal B of the battery over front contact a of code transmitter relay75CTRC, the back point of contact of relay ZWTFPR, to be described, thefront point of contact 0 of relay NLPR and through the winding of therelay to terminal N of the battery. It is thus apparent that relay ZWCRunder normal conditions follows the 75 code pulses of relay 75CTRC, thatis, relay ZWCR is picked up when relay 75CT RC closes its front contacta and is released when relay 75CT RC opens its front contact a in itscode generating cycles.

Relay ZWCR has a second operating circuit which extends from terminal Bof the battery over the front point of contact c of relay 2WTR, the backpoint of contact c of relay NLPR and through the Winding of the relay toterminal N of the battery. This circuit is employed for operation ofrelay ZWCR in generating reverse code as will be described later. Arectifier, reference 13, is connected across the winding of relay 2WCRat this time to slightly retard the release of the relay, in a mannerwell known in the art, when the release of relay ZWTR opens at the frontpoint of its contact c the second operating circuit for relay 2WCR. Thenegative terminal N of the battery is connected to the back point ofcontact c of relay ZWTR to provide further retardation of the release ofrelay ZWCR when relay ZWTR closes the back point of its contact 6.

A third circuit is provided for picking up relay 2WCR when it is desiredto apply a long normal code pulse to track section 2T under conditionsto be hereinafter described. This pickup circuit extends from terminal Bof the battery, over front contact 0 of relay ZWTFPR, front contact cofrelay NLPR and through the winding of relay ZWCR to terminal N of thebattery.

As set forth above relay 2WCR, under the normal status of the system asshown, is being operated at a code speed of 75 pulses per minute by thecoding action of contact a of relay 75CTRC. This operation of relay 2WCRsupplies code pulses of 75 code to the rails of track section 2T by afirst circuit extending from the positive terminal of track battery ZTBEover front contact a of relay 2WCR, the back point of contact a ofrelay2WTR and to the rail of track section 2T designated by theconventional plus sign; and by a second circuit extending from thenegative terminal of track battery ZTBE directly to the rail of tracksection 2T designated by the conventional minus sign. It is thusapparent that 75 code is normally being supplied to the rails of tracksec- 4 tion 2T at signal location ZWG and flows through said rails tothe intermediate signal location.

The control circuits for, and the operation of, the other apparatus atsignal 2WG location will be described later when normal code is beingtransmitted in the opposite direction.

Referring now to FIGS. 3 and 5, the operation of the apparatus at theintermediate signal location, when the 75 code flowing through the railsof track section 2T from signal location 2WG is received at saidintermediate location, will be described.

The winding of track relay ZETR (FIG. 3) is connected to the rails oftrack section 2T by a first circuit which extends from the right handside of the relay over back contact b of relay 2ECR, to be described,and to the rail of track section 2T designated by the conventional plussign; and by a second circuit which extends from the left hand side ofrelay ZETR directly to the rail of track section 2T designated by theconventional minus sign. Relay ZETR is also provided with a stickcircuit which extends from the positive rail through the front point ofcontact a of relay ZETR to the winding of the relay. It is thus apparentthat relay ZETR is picked up when relay 2ECR is released and a pulse ofcode is received over the track rails, and is retained picked up for theduration of the pulse by the stick circuit over the front point of itscontact a, regardless of the action of back contact b of relay 2ECRthereafter. Relay 2ETR is, therefore, normally following coded energyreceived from the rails of track section 2T.

The code following action of relay ZETR provides pickup circuits forrelays ZETFPR and EWHR shown in FIG. 3. The pickup circuit for relayZETFPR ex tends from terminal B of the battery over back contact [I ofrelay WSR, back contact a of relay ECCR, to be described, the frontpoint of contact b of relay ZETR, and through the winding of relayZETFPR to terminal N of the battery. The release time of relay ZETFPR issuificiently retarded by a rectifier snub 21 across the winding of therelay, that the relay will remain picked up during the normal off periodof the coded track energy when relay ZETR is released opening the frontpoint of its contact b. The use of such rectifier snubs to provideretardation of release time is well known to those versed in the art.Relay EWHR has a pickup circuit which extends from terminal B of thebattery over back contact d of relay WSR, back contact a of relay ECCR,the back point of contact b of relay ZETR, the back point of contact bof relay IWI'FPR, to be de scribed, the front point of contact b ofrelay ZETFPR and through the winding of relay EWHR to terminal N of thebattery. A capacitor-resistor unit, reference 23, is employed at thistime to maintain relay EWHR in the picked up position during the onperiods of the coded track pulses, that is, when the back point ofcontact b of relay 2ETR is open. This unit is connected in multiple withrelay EWHR when relay ZETFPR is energized due to the code followingaction of relay ZETR, and receives a storage of energy during the closedperiods of the back point of contact b of relay 2ETR. The circuit forcharging capacitor-resistor unit 23 may be traced from battery terminalB, over back contact d of relay WSR, over back contact a of relay ECCR,the back point of contact b of relay ZETR, the front point of contact aof relay ZETFPR, and through the unit to battery terminal N. During theopen period of the back point of contact [2 of relay ZETR, the charge ofenergy stored in unit 23 is discharged through relay EWHR over the frontpoint of contact a of relay ZETFPR and the previously described pickupcircuit for relay EWHR including the back point of contact b of relayIWTFPR. Relay EWHR is thus maintained in its picked up position duringthe open period of the back point of contact b of relay 2ETR in its codefollowing action. Whenever relay ZETFPR is released, a circuit iscompleted to dissipate the energy stored in unit 23 and cause immediaterelease of relay EWHR. This circuit extends from the left hand terminalof unit 23 over the back point of contact a of relay ZETFPR to the righthand terminal of unit 23. It is well to point out at this time thatrelay EWHR is a slow pickup relay to protect againstmomentary loss oftrack circuit shunt by a train traversing track sections IT or 2T.

There is shown in FIG. 5 the previously mentioned slow release relaywhich is employed at the intermediate signal location to determine thedirection of normal code being received, and which controls theoperation of my invention. This slow release relay is relay ECCR whichis provided with a rectifier snub, reference 29, to obtain the slowrelease feature by delaying the decay of flux through the winding of therelay. As shown in FIG. 3, under the normal status of the circuitsdescribed above relay ECCR is released.

Relay lWCR shown in FIG. 3 is the westward coding relay for tracksection IT and is following 75 code at this time. The circuit for codingIWCR at the 75 code rate extends from terminal B of the battery over theback point of contact 0 of relay IWTFPR, front contact a of codetransmitter relay 75CTRB, which is a relay similar to relay 75CTRC shownin FIG. 4 previously described, the front point of contact 0 of relayEWHR, back contact 0 of relay WSR, to be described, and through thewinding of relay IWCR to terminal N of the battery. Contact a of relayIWCR (FIG. 3) is supplying coded energy to track section IT at the 75code rate in a manner similar to the manner in which contact a of relayZWCR (FIG. 4), previously described supplies coded energy to tracksection 2T. This circuit for supplying coded energy to track section 1Textends from the positive terminal of track battery 1TBE over frontcontact a of relay IWCR, the back point of contact a of code followingtrack relay lWTR and to the rail of track section \lT designated by theconventional plus sign. The negative terminal of track battery ITBE isconnected directly to the rail of track section 1T designated by theconventional minus sign. It is thus apparent that the pickup of relayEWHR, by its pickup circuit previously described, allows relay lWCR tofollow 75 code and apply coded energy at the 75 code rate to tracksection 1T.

Relay IWTR, the code following track relay for track section IT at theintermediate signal location, is, at this time, following reverse codebeing received over the rails of track section 1T from lEG signallocation during the off periods of the normal code being supplied to therails by relay IWCR. The circuit for supplying this reverse code to therails of track section IT at lEG location will be described later, butit is desired to point out at present the reverse code following actionof relay lWTR. When relay IWCR is released during the oif period of thenormal code being supplied to track section IT, a circuit is completedfor connecting relay 1WTR to the rails of the track section. Thiscircuit extends from the plus rail of section 1T through back contact bof relay lWCR and through the winding of relay IWTR to the minus rail ofsection 1T. Thus, when an off period or normal code supplied to IToccurs, relay IWTR is connected to the rails to receive an on period ofreverse code.

Relay IWTFPR (FIG. 3) has a pickup circuit which extends from terminal Bof the battery over back contact e of relay ESR, back contact e of relayZETFPR, the front point of contact b of relay IWTR and through thewinding of relay IWTEPR to terminal N of the battery. Relay IWTFPR isalso provided with a rectifier snub 20 to snub the relay sufiiciently tobridge the open periods of contact b of relay 1WTR during the periodswhen relay IWTR is following normal code as will be hereinafterdescribed. At the present time relay IWTFPR re mains released due to itsabove described pickup circuit being open at back contact e of relayZETFPR. Thus 6 relay IWTFPR will not pick up when relay IWI-R isfollowing reverse code. a

Referring again to FIG. 5 there is shown a relay WTPR which is picked upwhen relay 1WTR is following reverse code. The pickup circuit for relayWTPR extends from terminal B of the battery over front contact 0 ofrelay IWTR and through the winding of relay WTPR to terminal N of thebattery. Relay WTPR is provided with a capacitor-resistor unit,reference 30, across its winding to sufl'iciently retard the releasetime of the relay to bridge the relatively long open periods of frontcontact 0 of relay IWTR in its reverse code following action. The use ofsuch capacitor-resistor units to provide a relatively long release timeof relays is well known in the art. Relay WTPR, therefore, remainspicked up during the code following action of relay IWTR in followingreverse code, or in following normal code as will be explained later. Itis thus apparent that the only time relay WTPR is released is when lWTRis not following code such as when track section IT is occupied by atrain.

The signals lEG, 1WG, ZEG and ZWG are shown in the drawings as being ofthe color-light type and the lighting circuit for signal ZEG is shown inFIG. 5. Signal 2EG is shown as having two lamps, green and red,designated by the reference characters ZEGGE and 2EGRE, respectively.The indications resulting from the illumination of the green or redlamps being illuminated individually are proceed and stop, respectively.Signal lWG is shown in a similar manner in FIG. 5 and has lampsdesignated IWGGE and IWGRE which give the same indications as thesimilar lamps of signal ZEG. The colors displayed and the indicationsgiven by signals lEG and ZWG will be described later.

Under the normal conditions of the circuits as described above a circuitis prepared for illumination of signal 2EG to display a green lamp andthus give a proceed indication. This circuit may be traced from backcontact b of relay WTPR over back contact d of relay IWTFPR, frontcontact 1 of relay EWHR, front contact h of relay 2ETFPR and through thefilament of lamp ZEGGE to terminal N of the battery. This circuit iscompleted when terminal B of the battery, connected to the movableportion of contact b of relay WTPR, is supplied to the circuit over theback contact b of that relay. This action occurs when a train enterstrack section IT and shunts the reverse code being transmitted fromsignal location lEG (as will be described later) thereby stopping thereverse code following action of relay IWTR and releasing relay WTPR. Itis thus apparent that signal ZEG is normally dark but is approachlighted when a train enters track section 1T.

As previously set forth, relay lWCR (FIG. 3) is supplying normal code totrack section 1T under the normal state of the circuits as shown in thedrawings. At signal -1EG location code following track relay lETR isfollowing the normal code pulses being received from the rails. As isobvious, the track circuit arrangement at this location, including relayIETR, contacts a and b of relay IECR, to be described, and track batterylTBW is identical to the track circuit arrangement of ZETR, contacts aand b of relay ZECR and track battery ZTBW at the intermediate signallocation, and a detailed description of the arrangement is unnecessary.Therefore, for the purposes of simplification of this description it issuflicient to state that relay IETR is following the normal code pulsesbeing received over the rails and a description of the supplying ofreverse code to the rails at signal location 1EG will be given.

Relays IETFPR and IEHR constitute the code detecting relays at signalLEG location, similar to relays ZWTFPR and ZWHR, respectively, at signalZWG location. Relay IETFPR has a pickup circuit which extends fromterminal B of the battery over the front point of contact b of relayIETR and through the winding of relay IETFPR to terminal N of thebattery. Relay IETFPR is provided with a rectifier snub across itswinding to maintain the relay picked up during the open periods of'thefront point of contact b of relayIETR in its code following action.Relay IEHR has a pickup circuit which extends from terminal B of thebattery over the back point of contact b of relay IETR, front contact bof relay IETFPR and through the winding of relay IEHR to terminal N ofthe battery. Relay IEHR is provided with a capacitor-resistor unit snub,reference 6, to retain relay IEHR picked up during the open periods ofthe back point of contact b of relay IETR in its code following action.Capacitor-resistor unit 6 has a charging circuit which extends fromterminal B of the battery over the back point of contact b of relaylETR, the front point of contact a'of relay IE'DFPR and through the unitto terminal N of the battery. The discharge circuit from this unitthrough the winding of relay IEHR extends from the left hand terminal ofthe unit over the front point of contact a of =1ETFPR, front contact bof IETFPR and through the winding of relay lEHR to terminal N of thebattery. A circuit is provided for quickly dissipating the energy storedin unit 6 when relay IETFPR is released. This circuit extends from theleft hand terminal of unit 6 over the back point of contact a of relayIETFPR and to the left hand terminal of the unit.

Coding relay lECR (FIG. 2) is supplying reverse code to track sectionII" as previously stated. The circuit for operating this relay at thistime extends from terminal B of the battery over the front point ofcontact c of relay IETR, the front point of contact of relay IETFPR andthrough the winding of the relay to terminal N of the battery. RelayIECR is thus picked up when relay lETR closes its front contact 0 oneach on pulse of the normal code received over track section 1T. Frontcontact a of relay lECR is thus closed to connect the positive terminalof track battery ITBW to the plus rail of track section 1T, but thiscircuit is open at the back point of contact a of relay IETR for theduration of each on pulse of the normal code as the stick circuit forrelay lETR over the front point of its own contact a maintains thatrelay picked up for the duration of each on pulse of normal coderegardless of the opening of the pickup circuit for relay IETR at theback point of contact b of relay IECR. At the end of each on pulse ofthe normal code relay lETR is released, opening at the front point ofcontact 0 of relay lETR the pickup circuit for relay IECR. However, asnubbing circuit for relay IECR including a snubbing rectifier,reference 8, and terminal N of the battery connected to the back pointof contact c of relay lETR, maintains relay IECR in a picked up positionfor short periods after the release of relay lETRduring the off periodsof the normal code. Reverse code is, therefore, supplied to the rails oftrack section 1T during the off periods of normal code, over frontcontact a of relay IECR and the back point of contact a of relay lETR.

Signal llEG, as previously stated, is a color-light signal. The signalis shown as having a yellow lamp IEGYE and a red lamp IEGRE, and theindications given by the individual illumination of these yellow and redlamps are caution and stop, respectively. The circuit for illuminationof the red lamp extends from terminal B of the battery over the backpoint of contact a of relay IEHR and through the filament of lamp IEGREtoterminal N of the battery. The circuit for illumination of the yellowlamp extends from terminal B of the battery over the front point ofcontact a of relay lEl-IR and through the filament of lamp IEGYE toterminal N of the battery. Under the normal condition of the apparatusshown-in the drawings signal lEG is, therefore, giving a cautionindication to allow a train to proceed pastthesig'n'al lEG inan eastwarddirection. For purposes of'simplicity the circuits showndo not provideforgiving a green indication on signal -1EG--but it Will-be*obvious tothoseskilled in the art that additional codes can be used to provideadditional indications in the manner well known in the art, but as theseadditional indications are not necessary for illustration of myinvention provisions therefore have not been shown.

Having thus described the operation of the part of the apparatusinvolved under the normal condition of the circuits illustrated, I willnow describe the operation of apparatus involved when the direction oftraffic through the track stretch shown is reversed to allow for awestbound train movement by the clearing of signals IWG and 2WG.

Referring again to FIG. 4 it will be well to first mention that signalZWG normally gives a stop indication as tralfic is normally aligned foran eastward train movement through the track stretch shown in thedrawings. Similarly to signal lEG, signal ZWG is a color-light signaland has a yellow lamp ZWGYE and a red lamp ZWGRE the individualillumination of which lamps gives caution and stop indications,respectively. The circuit for energizing lamp ZWGRE extends fromterminal B of the battery over the back point of contact a of relay ZWHRand through the filament of lamp ZWGRE to terminal N of the battery. Thecircuit for energizing lamp ZWGYE extends from terminal B of the batteryover the front point of contact a of relay ZWHR and through the filamentof lamp ZWGYE to terminal N of the battery.

When it is desired to reverse the direction of traffic through the trackstretch and clear signal ZWG, control lever FL in FIG. 4 is moved to itsL or left position. The movement of lever L from its R position opensthe pickup circuit for relay NLPR and that relay releases. The releaseof relay NLPR opens at the front point of its front contact c thepreviously described pickup circuit for relay ZWCR, the relay ceases tofollow code and, after the expiration of the retardation of the releasetime of relay ZWCR provided by its snubbing circuits, relay ZWCRreleases and remains in that position. The release of relay 2WCR opensat its front contact a the previously traced circuit for supplying codedenergy to track section 2T and removes the coded energy previouslysupplied to that track section.

The removal of coded track energy from track section 2T causes relayZETR at the intermediate signal location (FIGS. 3 and 5) to ceasefollowing code and that relay releases and remains so. The steadyrelease of relay ZETR opens the pickup circuit for relay ZETFPR at thefront point of contact b of relay ZETR and, after the effects of therectifier snub 21 have ceased, relay ZETFPR releases. The release ofrelay ZETFPR opens at its front contact b the previously traced pickupcircuit for relay EWHR which releases. The release of relay EWHR opensat its front contact c the pickup circuit for relay IWCR and that relayceases to follow the code action of front contact a of code transmitterrelay 75CTRB, and relay IWCR releases and remains in the releasedposition. Relay lWCR remaining in the released position removes fromtrack section 1T the normal code pulses previously applied thereto.

The removal of coded track energy from track section 1T causes relayIETR (FIG. 2) to cease following code, remain released, and open at thefront point of its contact b the pickup circuit for relay lETFPR whichsubsequently releases. The release of relay IETFPR opens at its frontcontact [2 the pickup circuit for relay IEHR which also releases. Therelease of relay IEHR transfers the energizing circuit for the lamps ofsignal IEG from the yellow lamp IEGYE to the red lamp IEGRE and signal1EG changes from a caution indication to a stop indication.

An additional relay 75CTRA is shown in FIG. 2. Relay 75CTRA is a codetransmitter relay similar to relay 75CTRC in FIG. 4 and no furtherdescription thereof is considered necessary. The release of relaylETFPRas'desci-ibed above closes a pickup circuit for 9 relay IECR whichcauses relay IECR to follow 75 code. This circuit extends from terminalB of the battery over front contact a of relay 75CTRA, the back point ofcontact c of relay lETFPR, and through the winding of relay 1ECR toterminal N of the battery. It is thus apparent that relay lECR begins tofollow the 75 code generated by relay 75CTRA, and applies to trackcircuit 1T over its front contact a and the back point of contact a ofrelay IETR normal 75 code pulses.

The previously described release of relay ZETFPR when relay ZETR ceasedfollowing code established the pickup circuit for relay IWTFPR,previously described, over back contact 2 of relay ZETFPR. Relay IWTFPRaccordingly picks up when relay IWTR begins to follow the normal codepulses being received over track circuit IT, and a second pickup circuitfor relay EWHR is completed. This pickup circuit for relay EWHR extendsfrom terminal B of the battery over back contact e of relay ESR, backcontact e of relay ZETFPR, the back point of contact b of relay IWTR,the back point of contact b of relay ZETFPR, the from point of contact bof relay IWTFPR, and through the winding of relay EWHR to terminal N ofthe battery. A capacitor-resistor unit, reference 22, is employed atthis time to maintain relay EWHR picked up when the back point ofcontact b of relay lWTR is open. The circuit for charging this unitextends from terminal B of the battery over back contact e of relay ESR,back contact e of relay 2ETFPR the back point of contact b of relay1WTR, the front point of contact a of relay IWTFPR and through the unitto terminal N of the battery. The circuit for discharging the storage inthe unit through the winding of relay EWHR and maintaining the relaypicked up, when relay IWTR opens the back point of its contact b,extends from the right hand side of the unit over the front point ofcontact a of relay IWTFPR and thence over the pickup circuit for relayEWHR, just described. Unit 22 also has a circuit for dissipating anyenergy stored therein when relay IWTFPR releases. This circuit extendsfrom the right hand side of the unit over the back point of contact a ofrelay IWTFPR to the left hand side of the unit.

The pickup of relay IWTFPR also closes a circuit for pickup of relayECCR shown in FIG. 5-. This circuit extends from terminal B of thebattery over the back point of contact c of relay 2ETR, back contact 1of relay ZETFPR, front contact 1 of relay IWTFPR and through the windingof relay ECCR to terminal N of the battery. There is shown in multiplewith front contact 1 of relay IWTFPR in the pickup circuit for relayECCR, a front contact e of relay WSR. The use of this contact. will I bebrought out later in the description.

The pickup of relay ECCR indicatw that any code received at theintermediate location from track section 2T will be reverse code and notnormal code as will become apparent later. The pickup of relay ECCRopens at back contact a of that relay the previously described pickupcircuit for relay ZETFPR. Therefore, when reverse code is received fromtrack section 2T, relay 2ETFPR will remain released and signal 2EGcannot clear for a train movement in the wrong direction.

The pickup of relays lWTFPR and EWHR also prepares the lighting circuitsfor signal 1WG to give a proceed indication instead of the redindication. This signal, similar to signal ZEG, is normally dark, one ofits lamps being illuminated when relay ETPR, to be described, isreleased. The circuit for energizing the green lamp IWGGE of signal 1WGextends from terminal B of the battery over back contact b of relayETPR, the back point of contact g of relay ZETFPR, the front point ofcontact e of relay EWHR, the front point of contact g of relay IWTFPRand through the filament of the lamp to terminal N of the battery. Thered lamp IWGRE of signal 1WG is energized by obvious circuits when relayETPR is released, over back contact b of relay ETPR, and the front pointof contact g of relay 2ETFPR, or the back point of contact e of relayEWHR, or the back point of contact g of relay IWTFPR. No detaileddescription of these circuits ls believed necessary.-

Relay ETPR is the approach lighting relay for signal lWG and is releasedonly when relay 2ETR is released for a period of time as when tracksection 2T is occupied by a train. The pickup circuit for relay ETPRextends from terminal B of the battery over the front point of contact 0of relay 2ETR and through the winding of relay ETPR to terminal N of thebattery. Relay ETPR is provided with a capacitor-resistor unit snub,reference 31, across its winding to provide the relay with a relativelylong release time after the opening of its pickup circuit. This releasetime is sulficiently long to bridge the open period of the front pointof contact 0 of relay 2ETR when that relay changes from following normalcode to following reverse code, or vice versa.

When relay EWHR picks up as set forth above for a westward trainmovement, that is, when normal code is being received at theintermediate signal location from track section IT, a circuit iscompleted for coding relay 2ECR to apply normal code to track section2T. This circuit extends from terminal B of the battery over the backpoint of contact d of relay ZETFPR, front contact b of code transmitterrelay 75CTRB, the front point of contact d of relay EWHR, front contactb of relay ECCR, back contact c of relay ESR, to be described, andthrough the Winding of relay ZECR to terminal N of the battery. It isthus apparent that relay 2ECR begins to follow the 75 code pulsesproduced by code transmitter relay 75CTRB, and supplies coded energy atthe 75 code rate to track section 2T over front contact a of relay 2EC-Rand the back point of contact a of relay 2ETR.

The 75 code being supplied to track section 2T as described above, isreceived at signal 2WG location and relay ZWTR begins to follow the codepulses completing a pickup circuit for relay ZWTFPR. This circuit may betraced from terminal B of the battery over the front point of contact bof relay 2WTR and through the winding of relay ZWTFPR to terminal N ofthe battery. Relay ZWTFPR is provided with a rectifier snub to retardthe release of relay ZWTFPR sufficiently to bridge the open periods ofthe front point of contact b of relay ZWTR in its code following action.

The pickup of relay ZWTFPR completes a pickup circuit for relay 2WHRwhich may be traced from terminal B of the battery over the hack pointof contact b of relay 2WTR, back contact b of relay NLPR, from contact bof relay ZWTFPR and through the winding of relay 2WHR to terminal N ofthe battery. A capacitor-resistor unit snub, reference 12, is providedto maintain relay 2WHR in its picked up position when the back point ofcontact b of relay 2WTR opens during its code following action. Thecharging circuit for this unit extends from terminal B of the batteryover the back point of contact b of relay 2WTR, the front point ofcontact a of relay ZWTFPR and through unit 12 to terminal N of thebattery. The discharge circuit from unit 12 through the winding of relayZWHR extends from the right hand side of the unit through the frontpoint of contact a of relay ZWTFPR and thence over the pickup circuitfor relay ZWHR, previously described, to terminal N of the battery. Acircuit for dissipating the energy stored in unit 12 when relay ZWTFPRis released extends from the right hand side of the unit through theback point of contact a of relay 2WT'FPR to the left hand side of unit12.

The pick up of relay ZWHR completes the energizing circuit of lamp ZWGYEof signal ZWG over the front point of contact a of relay ZWHR, and opensat the back point of contact a of relay ZWHR the energizing circuit forlamp ZWGRE of signal 2WG. Signal 2WG, therefore, now displays a yellowlamp and gives a caution indication.

The code following action of relay ZWTR star-ts relay ZWCR to operatingto generate reverse code pulses and supplying the pulses to tracksection 2T during the off periods of the normal code. This circuit foroperating relay ZWCR is the previously traced circuit including backcontact of relay NLPR and coding contact c of relay ZWTR. Relay ZWCR ispicked up during the on period of the normal code when relay ZWTR picksup and remain up for a short period after the release of ZWTR due to thesnubbing effect of rectifier 13 and the negative terminal of the batteryconnected to the back point of contact c of relay 2WTR. Therefore, afterthe release of relay ZWTR during the off period of the normal code, ashort pulse of reverse code is applied to track section 2T over frontcontact a of relay ZWCR and the back point of contact a of relay ZWTR.

The above described pulses of reverse code applied to track section 2Toperate relay ZETR at the intermediate signal location and relays ETPRand ECCR remain energized due to the intermittent closing of the frontand back points of contact 0 of relay ZETR. Relay ZETFPR cannot pick upbecause its pickup circuit is open at back contact a of relay ECCR, aspreviously mentioned, and relay IWCR cannot operate to supply code totrack section 1T because its pickup circuits are open at the back pointof contact c of relay IWTFPR and the front point of contact c of relayZETFPR. No reverse code is supplied beyond the intermediate signallocation, therefore.

I will now described the operation of the circuit and apparatusarrangement when the direction of trafiic is to be changed to itspreviously described normal direction, and will thereafter describe theoperation of the arrangement when trains move through the track stretch.

To change the direction of traffic through the track stretch in theeastward direction or the direction from left to right again, lever FLis moved from the L posi tion to the R position. Relay NLPR is picked upover its previously described pickup circuit over contact a of lever FL.The pickup of relay NLPR prepares circuits for applying a pulse ofnormal code to track section 2T at signal ZWG location, which pulse issomewhat longer than the normal pulses of normal code. The first ofthese circuits charges a capacitor-resistor unit, reference 11, on thenext pulse of normal code received from track section 2T when relay ZWTRis picked up. This circuit extends from terminal B of the battery overthe front point of contact b of relay ZWTR, the front point of con tacta of relay NLPR and through the capacitor-resistor unit 11 to terminal Nof the battery. The second circuit picks up relay ZWCR and extends fromterminal B of the battery over the front point of contact 0 of relayZWTFPR, the front point of contact c of relay NLPR and through thewinding of relay QWCR to terminal N of the battery. Relay 2WCR is thuspicked up to apply a pulse of code to track section 2T over frontcontact a of relay ZWCR and back contact a of relay ZWTR, when relayZWTR releases upon the termination of the previously mentioned pulse ofcode supplied to relay ZWTR from track section 2T. Relay ZWTR opens itsstick circuit over the front point of its own front contact a and canreceive no more pulses of code from track section 21 until back contactb of relay ZWCR is closed. However, the opening of the front point ofcontact b of relay ZWTR permits the capacitor-resistor unit 11 todischarge its storage through the winding of relay ZWTFPR and this relayremains picked up for a relatively long period of time although itspickup circuit is open at the front point of contact I) of relay ZWTR.Relay ZWCR thus remains picked up until relay ZWTFPR releases and opensthe front point of its contact 0. It is, therefore, apparent that arelatively long pulse of code is applied to track section 2T over frontcontact a of relay. ZWCR. It is well to point out at this timethat unit11 has a circuit for dissipating any storage contained 12 therein, whenrelay' NLPR is released. This circuit extendsfrom the right hand side ofthe unit over the back point of contact a of relay NLPR to the left handside of the unit. It should also be pointed out that when relay NLPR isreleased unit 11 can have no effect on relay ZWTFPR.

When the snubbing effect of the storage in capacitorresistor unit 11being supplied to the winding of relay ZWTFPR wears off, relay ZWTFPRreleases and the winding of relay ZWCR is connected to the codingcontact a of relay 75CTRC, relay ZWCR begins to follow 75 code, andsupplying normal code pulses to track section 2T. The pickup of relayNLPR as mentioned above, also opens at its back contact b the pickupcircuit for relay ZWHR which releases changing the energizing circuitsfor the lamps of signal ZWG from the yellow lamp ZWGYE to the red lampZWGRE. Signal ZWG thus gives a stop indication.

The long pulse of normal code supplied to track section 2T as set forthabove, overrides the pulses of normal code being supplied to tracksection 2T at the intermediate signal location as relay ZETR, when relay2ECR releases during an off pulse of code, is picked up by the longpulse of normal code and remains up for the duration of the long pulse.Relay ZECR, therefore, can no longer supply normal code to track section2T as the circuit for so supplying the code is open at the back point ofcontact a of relay 2ETR.

Relay ZETR is held up for a suflicient period of time by the long pulseof code received, that the effect of the rectifier snub 29 across thewinding of relay ECCR disappears and relay ECCR releases. The release ofrelay ECCR closes the pickup circuit for relay ZETFPR over back contacta of relay ECCR and relay ZETFPR is picked up. The pickup of relayZETFPR opens at the back point of its contact b the pickup circuit forrelay EWHR which releases. The release of relay ECCR also opens at itsfront contact b the pickup circuit for relay ZECR and that relay ceasesto follow the code generated by contact b of relay 75CTRB. Thus normalcode is no longer applied to track section 2T by the operation of relayZECR.

The pickup of relay ZETFPR and the release of relay EWHR picks up relayIWCR to supply a long pulse of normal code to track section 1T whenrelay IWTR is released during the next off pulse of code received fromtrack section '1T. This circuit for picking up relay IWCR extends fromterminal B of the battery over the front point of contact 0 of relayZETFPR, the back point of contact a of relay ESR, the back point ofcontact 0 of relay EWHR, back contact 0 of relay WSR and through thewinding of relay IWCR to terminal N of the battery. Thus relay IWCR ispicked up and supplies a pulse of code to track section 1T over itsfront contact a and the back point of contact a of relay IWTR when relayIWTR releases during the off pulse of the code received from tracksection 1T. Relay lWTR cannot pick up on the next on pulse of code fromtrack section 1T since relay IWCR remains picked up, and the pickupcircuit for relay IWTR is open at back contact b of relay IWCR. Whenrelay ZETFPR picked up as described above, the pickup circuit for relayIWTFPR was opened at back contact 6 of relay ZETFPR. However, due to theeffect of the rectifier snub 20 across the wind mg of relay lWTFPR, therelay does not immediately release. Accordingly, relay IWCR remainspicked up until relay IWTFPR releases to establish the pickup circuitfor relay EWHR over the back point of contact b of relay IWTFPR and thefront point of contact b of relay ZETFPR. Relay EWHR is again picked upand the coding circuit for relay IWCR is again completed over the frontpoint of contact 0 of relay EWHR. Relay IWCR accordingly follows the 75code pulses supplied-by contact'a of relay 75CTRB, and supplies pulses13 of 75 code to track section 1T over its front contact a.

The pickup of relay ZETFPR as described above opened at the back pointof its contact g the circuit for lamp IWGGE of signal 1WG and preparesthe circuit for lamp IWGRE of that signal over the front point of itscontact g. The transfer of contact h of relay Z'ETFPR from its backpoint to its front point changes a circuit for signal ZEG from its redlamp ZEGRE to its green lamp ZEGGE. The release of relay IWTFPR andpickup of relay EWHR finishes the preparation of the circuit for lampZEGGE over the back point of contact d of relay IWTFPR and the frontpoint of contact f of relay EWHR. The operation of these relays alsoopens the circuit for lamp ZEGRE at the front point of contact d ofrelay IWTFPR and back point of contact 1 of relay EWHR.

The long pulse of code supplied to track section IT at the intermediatesignal location overrides the code being supplied to track section IT atsignal IEG location (FIG. 2) and track relay lETR picks up. The pickupof relay IETR disconnects contact a of relay IECR from the rails toprevent transmission of further normal code pulses from signal 'lEGlocation. The pickup of relay IETR also picks up relay IETFPR over thecircuit including the front point of contact b of relay =1ETR. Thepickup of relay IETFPR opens at the back point of its contact the codingcircuit over front contact a of relay 75CTRA, and closes at the frontpoint of its contact c the reverse coding circuit over the front andback points of contact c of relay IETR. When relay lETR releases at theend of the long normal code pulse and begins to follow the normal codepulses being received from track section 1T, relay IEHR is picked up tochange the indication given by signal 1EG from stop to caution. RelaylECR also begins to supply reverse code pulses to track section 1T overits front contact a and the back point of contact a of relay IETR. Thearrangement shown in the drawings is now again in its normal conditionpreviously described.

I Will now assume that the circuits are in their normal condition asshown, with signal IEG cleared for an eastward train movement throughthe track stretch. I will also assume that a train accepts signal IE6and enters track section IT.

The wheels and axles of the train entering track section 1T shunts boththe normal and reverse codes fiowing over the rails of track section 1T.At signal 1EG location relay IETR is released, releasing in turn relayIETFPR which releases relay IEHR. Signal IEG is thus controlled to giveits stop indication to any following train desiring to enter tracksection IT. The shunting of the reverse code by the train releases relaylWTR at the intermediate signal location and subsequently relay WTPRreleases after the effect of its snub 30 is gone. The release of WTPRcompletes the energizing circuit for lamp ZEGGE of signal 2EG over theback contact b of relay WTPR and the signal gives its proceed indicationfor the train to enter track section 2T when it arrives at signal ZEG.

The release of relay WTPR also completes a circuit .for picking updirectional stick relay ESR shown in FIG.

3. This circuit extends from terminal B of the battery over the frontpoint of contact d of relay ZETFPR, the back point of contact a of relayWTPR, front contact a of relay EWHR, the front point of contact a ofrelay ETPR and through the winding of relay ESR to terminal N of thebattery. When the train accepts signal ZEG and releases relay 2ETR byshunting the normal code flowing over track section 2T, relays ZETFPRand EWHR are also released in turn. The release of relay EWHR opens thejust described pickup circuit for relay ESR but a stick circuit forrelay ESR is closed to maintain relay ESR picked up. This circuitextends from terminal B of the battery over back contact b of relayEWHR, the back point of contact 12 of relay WSR,

the front point of contact b ofrelay ESR and through the winding ofrelay ESR to terminal N of the battery. Relay ESR is provided with aresistor snub, reference 25, across its winding to make the relaysufliciently slow release to bridge the transfer time from the openingof the pickup circuit for relay ESR at front contact a of relay EWHR, tothe closing of the stick circuit for relay ESR at the back contact b ofrelay EWHR.

The pickup of relay ESR establishes a circuit for coding IWCR at the 75code rate and supplying normal code to track section IT. This circuitextends from terminal B of the battery over the back point of contact 0of relay IWTFPR, front contact a of relay 75CTRB, the fiont point ofcontact a of relay ESR, the back point of contact c of relay EWHR, backcontact 0 ofrelay WSR and through the winding of relay IWCR to terminalN of the battery. It is thus apparent that relay IWCR again opcrates tosupply 75 code to track section 1T when relay ESR is picked up. I y a Itis desired to point out that, when the. train entered track section 1Tand released relay IETFPR as described above, relay IECR at signal lEGlocation is operated at the. 75 code rate by the circuit including theback point of contact 0 of relay IETFPR. The operation of relay IECRapplies normal code to track section 1T over front. contact a of relayIECR and the back point of contact a of relay 1ETR. This code is shuntedby the wheels and axles of the train occupying section 1T but followsthe train through the section. When the train vacates track section ITand is wholly within track sect-ion 2T, relay IWTR can follow the normalcode. pulses received but relay IWTFPR cannot pick up due to its pickupcircuit being open at back contact e of relay ESR. Therefore, relay EWHRcannot pick up and clear the improper signal 1WG. As described aboverelay IWCR is also operating to supply normal code to track section ITat this time. For a short period, therefore, the. two normal codes maybe supplied to track section 1T simultaneously, but the normal codebeing supplied at the intermediate signal location will eventually pickup relay lETR at signal lEG location. The pick up of relay 1ETR will inturn pick up relay IETFPR, remove the normal code supplied to tracksection IT at signal lEG location, and condition the apparatus at thatlocation to supply reverse code pulses to track section IT. The oppositeeffect cannot occur as relay IWTFPR at the intermediate signal locationcannot be picked up since its pickup circuit is open at back contact 2of relay ESR. The receipt of the normal code at signal lEG location andpickup of relay IETFPR, picks up in turn relay IEHR and signal lEG givesa caution indication for a train movement into track section IT for anysecond train that may be following the. first train described above.This second train could not, of course, proceed past signal ZEG untilthe first train has vacated track section 2T, as signal ZEG was operatedto give its stop indication when the first train entered track section2T releasing relays ZET'FPR and in turn relay EWHR. The circuit forenergizing the green lamp ZEGGE of signal 2EG is first opened at thefront point of contact h of relay ZETFPR and then at the front point ofcontact f of relay EWHR. The circuit for energizing the red lamp ZEGREof signal ZEG is first closed at the back point of contact h of relayZETFPR and then at the back point of contact 1 of relay EWHR. When thefirst train vacates track section 1T, relay WTPR is again picked up bythe reverse code following operation of track relay =1WTR and theintermittent closing of front contact 0 of that track relay. Theenergizing circuit for the red lamp of signal ZEG is, therefore, openedat back contact b of relay WTPR.

The back contact 0 of relay ESR in the pickup circuit' for relay ZECR,insures that relay ZECR cannot be op erated to supply code to tracksection 2T so long as the directional stick relay is picked up.

When the train described vacates track section 2T, the normal code beingfed to rails of track section 2T at signal 2WG location is no longershunted and is received at the intermediate signal location. Relay ZETRfollows the normal code pulses, relay ZETFPR picks up, and relay EWHRalso picks up to again establish the normal condition of the circuits.The pickup of relay EWHR opens at its back contact b the stick circuitfor relay ESR over the front point of its own contact b and relay ESRreleases. The pick-up of relay EWHR also changes the coding circuit forrelay IWCR from the circuit over the back point of contact c of relayEWHR and the front point of contact a of relay ESR, to the circuit overthe front point of contact of relay EWHR. The apparatus is thus nowreturned to its normal condition.

I will now assume that traffic is aligned for a westward train movementthrough the track stretch, lever FL having been moved to its L positionand signals 1WG and 2WG having been cleared, as previously described.

The acceptance of signal 2WG by the westbound train and the trainsentrance into track section 2T shunts the normal code being receivedover track section 2T from the intermediate signal location and relayZWTFPR and, in turn, relay ZWHR are released. Signal 2WG is operated togive its stop indication to any train that may be following the firsttrain. The reverse code being supplied to track section 2T at signal 2WGlocation is also shunted by the wheels and axles of the train and relay2ETR ceases to follow the reverse code pulses, and is released, in turnreleasing relay ETPR. Signal 1WG is approach lighted over the backcontact b of relay ETPR to energize signal lamp IWGGE of signal 1WG andgive the proceed indication of the signal.

The release of relay ETPR also picks up directional stick relay WSR by acircuit which extends from terminal B of the battery over the frontpoint of contact c of relay IWTFPR, the back point of contact a of relayETPR, front contact a of relay EWHR, the front point of contact a ofrelay WTPR and through the winding of relay WSR to terminal N of thebattery. When the train enters track section IT and shunts the normalcode being received at the intermediate signal location, relay IWTRceases to follow code, relay IWTFPR releases, in turn, releasing relayEWHR. The release of relay EWHR establishes a stick circuit for relayWSR. This circuit extends from terminal B of the battery over backcontact b of relay EWHR, the back point of contact [2 of relay ESR, thefront point of contact b of relay WSR, and

through the winding of relay WSR to terminal N of the battery. Relay WSRis thus maintained picked up so long as the westbound train occupiestrack section 1T. Relay WSR, similar to relay ESR, is provided with aresistor snub, reference 24, across its winding to maintain relay WSRpicked up during the transfer from its pickup circuit over front contacta of relay EWHR to its stick circuit over back contact b of relay EWHRand the front point of its own contact b.

When the westbound train first enters track section 1T, therebyreleasing relay IWTFPR as described above, the previously describedpickup circuit for relay ECCR is opened at front contact 1 of relay 1WlPPR. However, the multiple circuit for relay ECCR over front contact eof relay WSR having been previously closed when relay WSR picked up,relay ECCR remains in its picked up condition. Therefore, any codepulses received from track section 2T, when the train has vacated thattrack section and is Wholly within track section 1T, cannot operate topickup relay ZETFPR as its pickup circuit is open at back contact a ofrelay ECCR. Signal ZEG cannot, therefore, be cleared to give an improperindication.

The pickup of relay WSR also prepares a circuit for operating relay ZECRto supply normal code .p'ulses to track section 2T. This circuitextends"from terminal" B of the battery over the back point of contact d ofrelay ZETFPR, front contact b of relay CT RB, front contact a of relayWSR, the back point of contact d of relay EWHR (assuming the westboundtrain has entered track section II), front contact b of relay ECCR, backcontact 0 of relay ESR, and through the winding of relay 2ECR toterminal N of the battery. When the train has vacated track section 2T,therefore, the normal code pulses being supplied to track section 2Twill again be received at signal 2WG location to clear that signal forany train that may be following the first westbound train.

A back contact c of relay WSR is employed in the pickup circuit forrelay IWCR to insure that that relay cannot be operated to supply codeto track section 1T so long as relay WSR is picked up.

It should be pointed out that as long as relay NLPR at signal 2WGlocation remains released no normal code pulses are supplied to tracksection 2T in the rear of the westbound train traversing track section2T, as the operating circuit for relay ZWCR to supply normal code pulsesis open at the front point of contact 0 of relay NLPR. Therefore, thenormal code pulses supplied to track section 2T at the intermediatesignal location will be received at signal 2WG, when the train vacatessection 2T, with no interference from normal code pulses being suppliedin the other direction. However, if lever FL is returned to its Rposition, when the train is in section 2T, thereby picking up relayNLPR, normal code pulses are supplied to the rails of track section 2Tin the rear of the train. When the train vacates track section 2T thesecode pulses may operate relay 2ETR but relay ZETFPR cannot pick up asits pickup circuit is open at back contact a of relay ECCR. The normalcode pulses being supplied to track section 2T at the intermediatesignal location will eventually pick up relay ZWTR at signal 2WGlocation. The pick up of relay 2WTR will pick up relay ZWTFPR andcomplete the pickup circuit for relay ZWCR over the front point ofcontact 0 of relay ZWTFPR and the front point of contact 0 of relayNLPR. The release of relay ZWTR, during the next off period of thenormal code received from track section 2T, does not energize relay ZWHRas its pickup circuit is open at back contact b of relay NLPR. SignalZWHR is thus controlled to give its stop indication when relay NLPR ispicked up. The release of relay ZWTR closes at the back point of itscontact a the previously described circuit including front contact a ofrelay ZWCR for supplying the long pulse of normal code to track section2T. As long as relay ZWCR remains picked up the circuit from the trackrails to relay ZWTR is open at back contact b of relay ZWCR. RelayZWTFPR remains picked up, after the opening of the front point ofcontact b of relay ZWT R, by the previously described circuit from theright hand side of capacitorresistor unit 11 over the front point ofcontact a of relay NLPR and through the winding of relay ZWTFPR toterminal N of the battery. Maintaining relay ZWTFPR thus picked up for arelatively long period, maintains relay ZWCR picked up to supply theaforesaid long pulse of normal code to track section 2T.

The long pulse of normal code supplied to track section 2T beingreceived at the intermediate signal location picks up relay ZETR for theduration of the pulse. The pick up of relay ZETR opens at the back pointof its contact 0 the pickup circuit for relay ECCR which releases afterthe effects of its rectifier snub 29 have worn away. The duration of thelong pulse is greater than the delayed release time of relay ECCRprovided by the rectifier snub. The release of relay ECCR closes at theback contact a of relay ECCR the pickup circuit for relay ZETFPR but therelay remains released as its pickup circuit remains open at backcontact d of relay WSR. At signal 2WG location, when'the delayed releaseefiect of unit 11 have disappeared, relay ZWTFPR will release closingthe back point of its contact 0 and completing the coding circuit forrelay ZWCR. Relay ZWCR 13 of 75 code to track section 1T over-its frontcontact a.

The pickup of relay ZETFPR as described above opened at the back pointof its contact g the circuit for lamp IWGGE of signal 1WG and preparesthe circuit for lamp lWGRE of that signal over the front point of itscontact g. The transfer of contact h of relay 2ETFPR from its back pointto its front point changes a circuit for signal ZEG from its red lampZEGRE to its green lamp ZEGGE. The release of relay IWTFPR and pickup ofrelay EWHR finishes the preparation of the circuit for lamp ZEGGE overthe back point of contact d of relay IWTFPR and the front point ofcontact 1 of relay EWHR. The operation of these relays also opens thecircuit for lamp ZEGRE at the front point of contact d of relay IWTFPRand back point of contact 1 of relay EWHR.

The long pulse of code supplied to track section IT at the intermediatesignal location overrides the code being supplied to track section IT atsignal lEG location (FIG. 2) and track relay lETR picks up. The pickupof relay IETR disconnects contact a of relay IECR from the rails toprevent transmission of further normal code pulses from signal 1EGlocation. The pickup of relay IETR also picks up relay IETFPR over thecircuit including the front point of contact I) of relay IETR. Thepickup of relay IETFPR opens at the back point of its contact c thecoding circuit over front contact a of relay 75CTRA, and closes at thefront point of its contact the reverse coding circuit over the front andback points of contact 0 of relay IETR. When relay lETR releases at theend of the long normal code pulse and begins to follow the normal codepulses being received from track section 1T, relay IEHR is picked up tochange the indication given by signal 1EG from stop to caution. RelaylECR also begins to supply reverse code pulses to track section 1T overits front contact a and the back point of contact a of relay IETR. Thearrangement shown in the drawings is now again in its normal conditionpreviously described.

I will now assume that the circuits are in their normal condition asshown, with signal IEG cleared for an eastward train movement throughthe track stretch. I will also assume that a train accepts signal 1EGand enters track section IT.

The wheels and axles of the train entering track section 1T shunts boththe normal and reverse codes flowing over the rails of track section 1T.At signal lEG location relay lETR is released, releasing in turn relayIETFPR which releases relay lEHR. Signal 1EG is thus controlled to giveits stop indication to any following train desiring to enter tracksection IT. The shunting of the reverse code by the train releases relayIWTR at the intermediate signal location and subsequently relay WTPRreleases after the effect of its snub 30 is gone. The release of WTPRcompletes the energizing circuit for lamp ZEGGE of signal ZEG over theback contact b of relay WTPR and the signal gives its proceed indicationfor the train to enter track section 2T when it arrives at signal 2EG.

The release of relay WTPR also completes a circuit for picking updirectional stick relay ESR shown in FIG. 3. This circuit extends fromterminal B of the battery over the front point of contact d of relayZETFPR, the back point of contact a of relay WTPR, front contact a ofrelay EWHR, the front point of contact a of relay ETPR and through thewinding of relay ESR to terminal N of the battery. When the trainaccepts signal 2EG and releases relay ZETR by shunting the normal codeflowing over track section 2T, relays ZETFPR and EWHR are also releasedin turn. The release of relay EWHR opens the just described pickupcircuit for relay ESR but a stick circuit for relay ESR is closed tomaintain relay ESR picked up. This circuit extends from terminal B ofthe battery over back contact b of relay EWHR, the back point of contactb of relay WSR,

the front-point of contact b of relay ESR and through the winding ofrelay ESR to terminal Niof the battery.-

Relay ESR is provided with a resistor snub, reference 25, across itswinding to make the relay sufiiciently' slow release to bridge thetransfer time from the opening of the pickup circuit for relay ESR atfront coritact a of relay EWHR, to the closing of the stick circuit for.

relay ESR at the back contact b of relay EWHR.

The pickup of relay ESRestablishes a circuit for coding IWCR at the 75code rate and supplying normal code point of contact a of relay ESR, theback point of contact c of relay EWHR, back contact c of relay WSR andthrough the winding of relay IWCR to terminal N of the,

:battery. It is thus apparent that relay IWCR again operates to supply75 code to track section 1T when relay ESR is picked up.

It is desired to point out that,.when the train entered track section 1Tand released relay IETFPR as described above, relay lECR at signal 1EGlocation is operated at the 75 code rate by the circuit including theback point of contact 0 of relay IETFPR. The operation of relay IECRapplies normal code to track section 1T over front contact a of relayIECR and the back point of. contact a of relay IETR. This code isshunted by the wheels and axles of the train occupying section 1T butfollows the train through the section. When the train vacates tracksection IT and is wholly within track section 2T, relay IWTR can followthe normal code pulses received but relay IWTFPR cannot pick up due toits pickup circuit being open at back contact e of relay ESR. Therefore,relay EWHR cannot pick up and clearthe improper signal 1WG. As describedabove relay IWCR is also operating to supply normal code to tracksection IT at this time. For a short period, therefore, the two normalcodes may be supplied to track section 1T simultaneously, but the normalcode being supplied at the intermediate signal location will eventuallypick up relay lETR at signal lEG location. The pick up of relay lETRwill in turn pick up relay IETFPR, remove the normal code Supplied totrack section IT at signal IEG location, and condition the apparatus atthat location to supply reverse code pulses to track section IT. Theopposite effect cannot occur as relay IWTFPR at the intermediate signallocation cannot be picked up since its pickup circuit is open at backcontact e of relay ESR. The receipt of the normal code at signal lEGlocation and pickup of relay IETFPR, picks up in turn relay lEHR andsignal IEG gives a caution indication for a train movement into tracksection IT for any second train that may be following the first traindescribed above. This second train could not, of course, proceed pastsignal ZEG until the first train has vacated track section 2T, as signalZEG was operated to give its stop indication when the first.

train entered track section 2T releasing relays ZETFPR and in turn relayEWHR. The circuit for energizing the green lamp ZEGGE of signal 2EG isfirst opened at the front point of contact h of relay ZETFPR and then atthe front point of contact of relay EWHR. The circuit for energizing thered lamp ZEGRE of signal ZEG is first closed at the back point ofcontact h of relay ZETFPR and then at the back'point of contact of relayEWHR. When the first train vacates track section 1T, relay WTPR is againpicked up by the reverse code following operation of track relay !1WTRand the intermittent closing of front contact c of that track relay. Theenergizing circuit for the red lamp of signal ZEG is, therefore, openedat back contact b of relay WTPR.

The back contact 0 of relay ESR in the pickup circuit for relay 2ECR,insures that relay ZECR cannot be operated to supply code to tracksection 2T so long as the directional stick relay is picked up.

When the train described vacates track section 2T, the normal code beingfed to rails of track section 2T at signal ZWG location is no longershunted and is received at the intermediate signal location. Relay ZETRfollows the normal code pulses, relay ZETFPR picks up, and relay EWHRalso picks up to again establish the normal condition of the circuits.The pickup of relay EWHR opens at its back contact b the stick circuitfor relay ESR over the front point of its own contact b and relay ESRreleases. The pick-up of relay EWHR also changes the coding circuit forrelay IWCR from the circuit over the back point of contact of relay EWHRand the front point of contact a of relay ESR, to the circuit over thefront point of contact c of relay EWHR. The apparatus is thus nowreturned to its normal condition.

I will now assume that traffic is aligned for a westward train movementthrough the track stretch, lever FL having been moved to its L positionand signals 1WG and 2WG having been cleared, as previously described.

The acceptance of signal 2WG by the westbound train and the trainsentrance into track section 2T shunts the normal code being receivedover track section 2T from the intermediate signal location and relayZWTFPR and, in turn, relay ZWHR are released. Signal ZWG is operated togive its stop indication to any train that may be following the firsttrain. The reverse code being supplied to track section 2T at signal ZWGlocation is also shunted by the wheels and axles of the train and relayZET R ceases to follow the reverse code pulses, and is released, in turnreleasing relay ETPR. Signal 1WG is approach lighted over the backcontact b of relay ETPR to energize signal lamp IWGGE of signal 1WG andgive the proceed indication of the Signal.

The release of relay ETPR also picks up directional stick relay WSR by acircuit which extends from terminal B of the battery over the frontpoint of contact 0 of relay IWTFPR, the back point of contact a of relayETPR, front contact a of relay EWHR, the front point of contact a ofrelay WTPR and through the winding of relay WSR to terminal N of thebattery. When the train enters track section IT and shunts the normalcode being received at the intermediate signal location, relay IWTRceases to follow code, relay IWTFPR releases, in turn, releasing relayEWHR. The release of relay EWHR establishes a stick circuit for relayWSR. This circuit extends from terminal B of the battery over backcontact b of relay EWHR, the back point of contact b of relay ESR, thefront point of contact b of relay WSR, and through the winding of relayWSR to terminal N of the battery. Relay WSR is thus maintained picked upso long as the westbound trainoccupies track section 1T. Relay WSR,similar to relay ESR, is provided with a resistor snub, reference 24,across its winding to maintain relay WSR picked up during the transferfrom its pickup circuit over front contact a of relay EWHR to its stickcircuit over back contact b of relay EWHR and the front point of its owncontact b.

When the westbound train first enters track section 1T, therebyreleasing relay lWTFPR as described above, the previously describedpickup circuit for relay ECCR is opened at front contact 1 of relayIWTFPR. However, the multiple circuit for relay ECCR over front contacte of relay WSR having been previously closed when relay WSR picked up,relay ECCR remains in its picked up condition. Therefore, any codepulses received from track section 2T, when the train has vacated thattrack section and is wholly within track section 1T, cannot operate topickup relay ZETFPR as its pickup circuit is open at back contact a ofrelay ECCR. Signal ZEG cannot, therefore, be cleared to give an improperindication.

The pickup of relay WSR also prepares a circuit for track section 2T.Thiscircuit extends from terminal B of the battery over the back pointof contact d of relay ZETFPR, front contact b of relay CT RB, frontcontact a of relay WSR, the back point of contact d of relay EWHR(assuming the westbound train has entered track section 1T), frontcontact b of relay ECCR, back contact 0 of relay ESR, and through thewinding of relay ZECR to terminal N of the battery. When the train hasvacated track section 2T, therefore, the normal code pulses beingsupplied to track section 2T will again be received at signal ZWGlocation to clear that signal for any train that may be following thefirst westbound train.

A back contact c of relay WSR is employed in the pickup circuit forrelay IWCR to insure that that relay cannot be operated to supply codeto track section 1T so long as relay WSR is picked up.

It should be pointed out that as long as relay NLPR at signal ZWGlocation remains released no normal code pulses are supplied to tracksection 2T in the rear of the westbound train traversing track section2T, as the operating circuit for relay 2WCR to supply normal code pulsesis open at the front point of contact 0 of relay NLPR. Therefore, thenormal code pulses supplied to track section 2T at the intermediatesignal location will be received at signal 2W6, when the train vacatessection 2T, with no interference from normal code pulses being suppliedin the other direction. However, if lever FL is returned to its Rposition, when the train is in section 2T, thereby picking up relayNLPR, normal code pulses are supplied to the rails of track section 2Tin the rear of the train. When the train vacates track section 2T thesecode pulses may operate relay ZETR but relay ZETFPR cannot pick up asits pickup circuit is open at back contact a of relay ECCR. The normalcode pulses being supplied to track section 2T at the intermediatesignal location will eventually pick up relay ZWTR at signal ZWGlocation. The pick up of relay ZWTR will pick up relay ZWTFPR andcomplete the pickup circuit for relay 2WCR over the front point ofcontact 0 of relay ZWTFPR and the front point of contact 0 of relayNLPR. The release of relay ZWTR, during the next off period of thenormal code received from track section 2T, does not energize relay ZWHRas its pickup circuit is open at back contact b of relay NLPR. SignalZWHR is thus controlled to give its stop indication when relay NLPR ispicked up. The release of relay ZWTR closes at the back point of itscontact a the previously described circuit including front contact a ofrelay 2WCR for supplying the long pulse of normal code to track section2T. As long as relay 2WCR remains picked up the circuit from the trackrails to relay ZWTR is open at back contact 12 of relay 2WCR. RelayZWTFPR remains picked up, after the opening of the front point ofcontact I) of relay ZWFR, by the previously described circuit from theright hand side of capacitorresistor unit 11 over the front point ofcontact a of relay NLPR and through the winding of relay ZWTF PR toterminal N of the battery. Maintaining relay ZWTFPR thus picked up for arelatively long period, maintains relay 2WCR picked up to supply theaforesaid long pulse of normal code to track section 2T.

The long pulse of normal code supplied to track section 2T beingreceived at the intermediate signal location picks up relay ZETR for theduration of the pulse. The pick up of relay ZETR opens at the back pointof its contact 0 the pickup circuit for relay ECCR which releases afterthe effects of its rectifier snub 29 have worn away. The duration of thelong pulse is greater than the delayed release time of relay ECCRprovided by the rectifier snub. The release of relay ECCR closes at theback contact a of relay ECCR the pickup circuit for relay ZETFPR but therelay remains released as its pickup circuit remains open at backcontact d of relay WSR. At signal 2WG location, when the delayed releaseeffect of unit 11 have disappeared, relay ZWTFPR will release closingthe back point of its contact c and completing the coding circuit forrelay 2WCR. Relay 2WCR follows the 75 code pulses of relay 75CTRC andsupplies normal code to track section 2T. Relay ZETR at the intermediatesignal location follows the normal .code pulses but relay ZETFPR remainsreleased as relay WSR is still picked up. The release of relay ECCRopened at its front contact b the coding circuit for relay ZECR andthatrelay ceases to follow 75 code and ceases to supply normal code totrack section 2T.

I will now first assume that the westbound train traverses track section1T and vacates that section with lever FL remaining in its L position.When the train vacates track section'lT, the normal code pulses beingsupplied to track section IT by the code following action of relay IECRare again received at the intermediate signal location and relay IWTRwill again follow normal code. Relay IWTFPR will be picked up over itspickup circuit including back contact e of relay ZETFPR. The pick up ofrelay IWTFPR will complete the pickup circuit for relay EWHR includingthe 'back point of contact b of relay ZETFPR and the front point ofcontact b of relay 1W I-PPR. Relay EWHR will pick up opening at itsbackcontact b the stick circuit for relay 'WSR which will also releaseopening at its front contact 2 the multiple pickup circuit for relayECCR. However, the circuit for relay ECCR over front contact f of relay1WTFPR, having been previously closed, relay ECCR remains picked up. Thepick up of relay EWHR, as described above, also opened the codingcircuit for relay ZECR over the back point of contact d of relay EWHRand front contact a of relay WS'R, but closed at the front point of itscontact d the multiple coding circuit for relay ZECR. Relay ZEOR,therefore, continues to operate and supply normal code to track section2T. The apparatus at signal ZWG location also continues to supplyreverse code to track section'2T.

I will now assume that when the westbound train vacates track section1T, lever NLPR had previously been returned to its'right hand or Rposition. The circuits are, therefore, operating in the mannerpreviously described for 'thiscondition. When the 'trainvacates tracksection 1T, the normal code being supplied to tracksection11T at signal1EG location is no longer shunted'an'd is received at the intermediatesignal location; Relay 1W'IR fo'llows the code, relay IWTFPRpiks upandconsequently relay EWHR picks up. The pickup of relay EWHR opens atits back contact b the stick circuit for relay 'WSR which releases. Therelease of relay WSR closes at its back contact d the pickup circuit forrelay ZETFPR which picks up, opening at its back contact 1; the pickupcircuit for relay "IWTFPR, and at the back point of its contact b thepickup'c'ircuit for relay EWHR. Relay 1WTFPR releases and the pickupcircuit for relay EWHR over the front point of contact '5 of relay Z E'IFPR and the 'back point of contact b of relay 1W DFPR, is closed. RelayEWHR again picks up and signal 2136 is cleared for an eastbound move.

The previously described pickup of relay EWHR and consequential releaseof relay WSR prepared the coding circuit for relay lWCR. However thiscircuit remained open at the front contact of relay 1W 1 FPR. When relayZETFP'R opens its back contact 2 as described and releases relays lWTFPRand EWHR but subsequently again picks up relay EWHR over the front pointof contact b of relay ZETFPR, the coding circuit for relay IWCR is againcompleted. Relay 1WCR supplies over the circuit including its frontcontact a normal code to track section 1T simultaneously with the normalcode being supplied to track section 1T at signal 1EG location. However,relay IWTFPR at the intermediate signal location is prevented frompicking up by the open back contact 2 of relay ZETFPR. There is nothingat signal 1EG location to prevent relay lETFPR from picking up whenrelay l-ETR is picked up by a pulse of normal code. Eventually,therefore, relay IE'TR will receive a pulse of normal code, relay lETFPR will pick up and the normal code being supplied to track section nowreturned to its normal condition .with signals lEG and 'ZEG cleared foreastbound train movements.

From this description it is apparent that with apparatus of my inventionas shown in the drawings, I have provided an arrangement at anintermediate signal location whereby normal and reverse codes receivedin either direction are distinguished from each other, and the propertraffic controlling devices or signals are operated by the receipt ofthe normal code only.

Although I have herein shown and described only one form of apparatusembodying my invention, it will be understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is.

1. In arailway traflic control system for a stretch of railway trackextending between a first location and a second location and comprisingtwo adjoining track sections over which 'traflic may at times movein afirst-direction and at other times move in a second-direction oppositeto said first direction, the-combination comprising,

'an intermediate location in said stretch at the junction of said firstand second track sections, means for supplying for said first directionof trafllc normal code pulses of energy to the rails of said secondtrack section at said second location, afirst code following relayconnected to the rails of saidsecond-track section at said intermediatelocation, a first slow release relay at said intermediate location,means controlled by said code following relay for picking up said-slowrelease relay when the code following relay is following normal codepulses of energy, means controlled by said slow release relay in itspicked up position for supplying normal code pulses of energy to therails of said first track section at said intermediate location, -a codefollowing relay-connected to the rails'of said first track section atsaid first location, means operrails of said first track section at saidintermediate loca tion, a second slow release relay at said intermediatelocation, means for supplying for said second direction of traificnormal code pulses of energy to the rails of said first track section atsaid first location, means controlled "by said secondcode followingrelay at said intermediate location for picking up said second slowrelease relay when the 'code following relay is following normal codepulsesof energy, a 'third slow release relay at 'saidintermediatelocation, means controlled by said second slow release relay in itspicked up position and said first code following relay at saidintermediate location in its released position for picking up said thirdslow release relay,

means controlled by said third slow release relay in its picked upposition for maintaining said first slow release relay released, meanscontrolled by said second and third slow release relays both in theirpicked up position for supplying normal code pulses of energy to therails of said second track section at said intermediate location, a codefollowing relay connected to the rails of said second track section atsaid second location, means operating to supply reverse code pulses ofenergy to the rails of said second track section at said second locationduring the off periods of the normal code pulses of energy received fromsaid rails by said code following relay at said second location, meansfor supplying a code pulse of energy of a longer duration than a normalcode pulse of energy to the rails of said second track section at saidsecond location when said direction of trafiic is changed from saidsecond direction to said first direction, and means controlled by saidfirst code following relay at said intermediate location in its pickedup position in response to said code pulse of energy of a longerduration for releasing said third slow release relay at saidintermediate location.

2. In a railway traffic control system for a stretch of railway trackincluding first and second adjoining track sections electricallyinsulated from each other and through which trafiic moves in that orderfor a first direction of traflic between first and second locations inthe stretch and in the opposite order for a second direction of trafficbetween said locations, the combination comprising; means for supplyingto the rails of the second section at said second location normal codepulses for said first direction of trafiic, reverse code pulses for saidsecond direction of traffic, and a code pulse of a longer duration thana normal code pulse for changing the direction of tratfic from thesecond direction to the first direction; means for supplying to therails of the first section at said first location normal code pulses forsaid second direction of trafiic and reverse code pulses for said firstdirection of trafiic, first and second code responsive devices connectedacross the rails of said first and second track sections respectively atthe junction of the sections; first, second, and third slow releaserelays at said junction; means controlled by said first device and saidsecond relay for energizing said first relay only when the first deviceis energized by code pulses received from the rails of the first tracksection and the second relay is released, means controlled by said firstand second relays for energizing said third relay when the first relayis energized and the second relay is released, means controlled by saidthird relay and said second device for energizing said second relay onlywhen the third relay is released and the second device is energized bycode pulses received from the rails of the second track section; andmeans controlled by said second device, in response to said code pulseof a longer duration, for deenergizing said third relay following aperiod of energization thereof.

3. -In a railway trafiic control system for a stretch of railway trackincluding first and second adjoining track sections electricallyinsulated from each other and through which trafiic moves in that orderfor a first direction of traflic between first and second locations inthe stretch and in the opposite order for a second direction of trafficbetween said locations, the combination comprising, means for supplyingto the rails of the first section at said first location reverse codepulses for said first direction of trafiic and normal code pulses forsaid second direction of traffic; means for supplying to the rails ofthe second section at said second location reverse code pulses for saidsecond direction of traffic, normal code pulses for said first directionof trafiic, and a code pulse t 20 of a longer duration than a normalcode pulse to effect a change in the direction of traflic from saidsecond direction to said first direction; first and second codefollowing devices connected across the rails of said first and secondsections respectively at the junction of the sections; first, second,and third slow release relays at said junction; means controlled by saidsecond relay in its released position and by said first device in itscode following condition for energizing said first relay, meanscontrolled by said third relay in its deenergized position and saidsecond device in its code following condition for energizing said secondrelay, means controlled by said first relay in its energized positionand said second relay in its released position for energizing said thirdrelay; and means controlled by said second device, energized in repsonseto the receipt of said pulse of a longer duration, for deenergizing saidthird relay following a period of energization of that relay.

4. In a railway trafiic control system for a stretch of railway trackincluding first and second adjoining track sections electricallyinsulated from each other through which traffic moves in that order fora first direction of traflic and in the opposite order for a seconddirection of tratfic, the combination comprising, means for supplying tothe rails of said first track section at the entrance end thereof forsaid first direction of traflic reverse code pulses and at the exit endthereof for said second direction of traffic normal code pulses; meansfor supplying to the rails of said second track section at the entranceend thereof for said second direction of trafiic reverse code pulses; atthe exit end thereof for said first direction of trafiic normal codepulses, and at the entrance end thereof for said second direction oftrafic a code pulse of a longer duration than a normal code pulse whenit is desired to change the direction of trafiic from the seconddirection to the first direction; first and second code responsivedevices connected to the rails of said first and second track sectionsrespectively at the juncture thereof; first, second, and third relays atsaid juncture; means controlled by said first device and said secondrelay for energizing said first relay when the device responds to codepulses received from the rails of the first track section and the secondrelay is released, means controlled by said first and second relays forenergizing said third relay when the first relay is energized and thethird relay is released, means controlled by said third relay and saidsecond device for energizing said second relay only when the third relayis released and the second device responds to code pulses received fromthe rails of the second track section; and means controlled by saidsecond device for deenergizing said third relay, following a period ofenergization thereof, when the second device responds to said code pulseof a longer duration.

No references cited.

